Animal Body Systems Lecture 9 PDF

Biol 224.3 – Animal Body Systems Lecture 9: Post-Synaptic Electrophysiology, The ANS, & Evolution of Nervous Systems Dr Joan Forder Supplementary Reading: Textbook (5th Edition, Chapter 42, page 1159-1164, 1171-1175)...

Biol 224.3 – Animal Body Systems Lecture 9: Post-Synaptic Electrophysiology, The ANS, & Evolution of Nervous Systems Dr Joan Forder Supplementary Reading: Textbook (5th Edition, Chapter 42, page 1159-1164, 1171-1175) 1 Where we are headed Post-synaptic Electrophysiology Functional Divisions of the Nervous System The Autonomic Nervous System Sympathetic NS Parasympathetic NS Evolution of the Nervous System Post-synaptic Electrophysiology Ions move across post-synaptic membrane due to neurotransmitter binding to receptor Cause an electrotonic potential (EP) in dendrites of post-synaptic neuron Flows along membrane surface to axon hillock NOTE: EP from dendrites called a post-synaptic potential (PSP) 3 Post Synaptic Potentials At the hillock, the PSP will…. Depolarize or hyperpolarize the membrane Depends on the type of receptor/ion channel in the dendrite: a Na+ channel will let Na+ flow inward - causes a depolarizing or excitatory PSP (EPSP) a K+ channel will let K+ flow outward - causes a hyperpolarizing or inhibitory PSP (IPSP) a Cl- channel will let Cl- flow inward - causes a hyperpolarizing or inhibitory PSP (IPSP) 4 PSP’s are Graded Potentials EPSPs and IPSPs are EPSP IPSP called graded potentials (not all or none like APs) Size of PSPs at each receptor depend on amount of neurotransmitter released 5  Postsynaptic Neurons Receive MANY Inputs Caterpillar sensory neuron: yellow = synaptic contacts with postsynaptic neuron Fig 42.43 Up to 1,000 inputs onto post-synaptic neuron 6 Summation of PSPs Fig 42.44 Summation of subthreshold PSPs Summation can involve EPSPs and IPSPs occurs at axon Occurs in time and space hillock Important for processing inputs, learning, memory 7 Overview of Neuronal Signaling Physiology EPSP IPSP Synaptic Transmission EP EPSP Action IPSP Potential 8 Post Synaptic Regulation All Neurons have the same basic electrophysiology But, diversity of post-synaptic regulation possible through: many, many synaptic inputs per effector a wide variety of neurotransmitters different receptors proteins several intracellular signaling pathways Allows a nervous system to regulate/coordinate virtually all cellular physiology. 9 Summary All these activities depend on bioelectricity (afferent) Bioelectricity is defined as: the electrical Integration is the synthesis activity that occurs of an output based on the within living organisms. sum of the inputs It's a result of the (efferent) movement of charged particles called ions in and out of cells 10 Functional Divisions Somatic - voluntary control Autonomic - involuntary control Sympathetic whole body “flight & fight” Parasympathetic organ specific “rest and digest” see Fig 42.54 11 The Autonomic Nervous System (ANS) most tissues innervated by both divisions are two efferent neurons & peripheral ganglia integration also occurs in ganglia Fig 42.55 12 The ANS Divisions SYMPATHETIC DIVISION: preganglionic neuron more wide-spread (whole body) effects PARASYMPATHETIC DIVISION: postganglionic neuron more organ specific effects Fig 42.55 13 Functions of the ANS Sympathetic division Parasympathetic division Relaxes (inhibits) Constricts airways (stimulates) airways Increases heartbeat and Slows heartbeat force of contraction (inhibits) (stimulates) Inhibits digestion and Stimulates digestion stomach activity and stomach activity Fig 42.55 neurochemistry explains physiology Tissue-specific response depends on neurotransmitter & type of receptor in effector cell 14  Neurotransmitters & Receptors of The ANS Sympathetic division Parasympathetic division Preganglionic fibers: Preganglionic fibers : acetylcholine / acetylcholine / nicotinic receptor nicotinic receptor Postganglionic fibers: Postganglionic fibers: norepinephrine / acetylcholine / adrenoceptors Fig 42.55 muscarinic receptors 15  ANS Divisions have Antagonistic (Opposing) Effects Sympathetic: Parasympathetic: more active when body energy more active when body energy stores stores need to be used are being conserved / restored “flight & fight” system “rest & digest” system example: example: NOR via -adrenoceptor Ach via M3 receptor inhibits digestive tract stimulates digestive tract stimulates heart inhibits heart NOR via -adrenoceptor Ach via M2 receptor 16 The ANS Activity Both divisions are always activated Overall effect depends on which division is more active example physiology: inhibits digestive tract example physiology: stimulates heart stimulates digestive tract inhibits heart 17 The ANS Activity Both divisions are always activated Overall effect depends on which division is more active example physiology: stimulates digestive tract example physiology: inhibits heart inhibits digestive tract stimulates heart 18  ANS Summary a major source of integration in body used to regulate & coordinate majority of organ systems extensive feedback loops maintain body homeostasis Fig 42.55 19  Pressures on Nervous System Development Nervous systems of all animals are designed to provide optimum functioning Organization of nervous systems in different groups of invertebrates and vertebrates reflects differences in lifestyle and habitat. Nervous system evolution in animals Sponges: no neurons but still have basic cell physiology. Ganglia: collections of neuronal cell bodies = sites of integration Cephalization: concentration of neurons/ganglia in Fig 42.45 a “head” region 21  Nervous system evolution in animals Fig 42.45 Cnidarian have Nerve Planarians contain a pair of Echinoderms have more Nets that occur ganglia that form a small organization. throughout the animal. brain (cephalization). Nerve Ring & Radial No axons or dendrites. Ganglia connected by Nerves APs and Synapses all nerve cords. Still no Cephalization. over each neuron. Nerve Net throughout Limited processing. Limited processing. rest of body. Sensory processing.22  Nervous system evolution in animals Fig 42.45 Arthropods have a head Mollusc have neurons region that contains the clustered into paired Vertebrates have complex brain. ganglia connected by nervous systems. Brain has dorsal and major nerves. CNS: Brain and spinal ventral pairs of ganglia. Connected by major cord. Major sensory nerves Highly cephalized structures Complex, lobed brain Rapid processing. Ganglia in each segment Rapid processing. 23 Nervous system evolution in chordates Brain regions are conserved and modified Selective pressure drives relative representation of brain processing regions in Fig 42.48 different groups 24 The mammalian nervous system - an example of complexity Fig 42.46 Folding increases surface area (# of neurons/synapses) Know the chart above the figure in text 25 Development of the Human Brain Fig. 42.46, p. 1163  An Example of Complexity The mammalian nervous system Brain divided into functional regions Fig 42.50 27 Functional Divisions of the Vertebrate Nervous System Fig 42.54 28